Lead-in for electric currents in gas discharge vessels



March 22, 1960 B. BERGHAUS ErAL 2,929,947

LEADIN FOR ELECTRIC 'CURRENTS IN GAS DISCHARGE VESSELS Filed Feb. 17, 1954 2 Sheets-Sheet l W Y 2 W m wj 1 9401 6 4 D; 87 M 4% z M %A/// w March 22, 1960 B. BERGHAUS ETAL 2,929,947

LEAD-IN FOR ELECTRIC CURRENTS IN GAS DISCHARGE VESSELS Filed Feb. 17. 1954 2 Sheets-Sheet 2 INVENTORS BERNHARD BERGHAUS, HANS BUCEK ATTORNEY LEAD-1N FOR ELECTRIC CURRENTS 1N GAS DISCHARGE VESSELS Bernhard Berghaus and Hans Bucek, Zurich, Switzerland, assignors to Elektrophysikalische Anstalt, Bernhard Berghaus, Vaduz, Liechtenstein Application February 17, 1954, Serial No. 410,934

2,929,947 I Patented .Mar. 22, 1 960 rying out chemical reactions by means of high intensity Claims priority, application Switzerland February 17, 1953 p Claims. (Cl. 313-19) It is known to provide narrow long gaps in a current lead-in for metal gas discharge vessels in order to protect the insulation against the destroying elfect of the gas dis: charge. These known gaps are made so narrow that a discharge can no longer occur. However, in the case of high discharge pressures it is very difiicult, and even impossible to produce the required very narrow gaps in practice. It has therefore also been proposed to provide these gaps with laterally branched off annular gaps also in order to counteract the production of a flash-over.

In spite of all these measures, however,'the reliability of operation is still endangered by undesirable flash-overs and destruction of the insulating material, more particularly when working at high pressures. The present invention has enabled these protecting gaps to be further improved and to produce a current lead in, the reliability of operation of which is ensured over long periods of time.

The invention consists in the arrangement of a gap between metal parts of different potentials in glow-discharge vessels, which gap is of constant width over a portion of its length and which is gradually widened to an enlarged space, the length of the widened part being at least twice the width of the part of the gap of constant width. Preferably, the width of the gap at its widest part is a multiple of the width of its narrowest part. According to the invention, it is especially advan tageous for the gap to open with its part of substantially constant width into an adjacent gap. The said substantially wider space may open into an additional gap which has substantially the same width as the part of the gap of constant width. Moreover, according to a preferred construction of the gap according to the invention, the width of the gap increases towards the interior of the vessel. In the case of circular constructional parts, which come more particularly into question for such a current lead-in, this construction leads to annular funnel-like enlargements. It has been found that, in the case of gaps constructed according to the invention, effects are obtained which can be explained on the electrodynamic principle, as for instance in the case of the operation of the horn arrester. It was noticed during practical operation that discharge phenomena occurred at the base of the funnel which moved in the direction of the gap enlargement without having any effect so that they did not cause any disturbance during the operation. Moreover, the gap is advantageously obtained by means of concentric walls of the metal parts in such a way that it abuts at its end against the insulating material. However, the gap may also be continued beyond the contact with the insulating material.

The invention is illustrated by way of example in the accompanying drawings, wherein- Fig. 1 is a vertical section of a current lead-in for glow discharge vessels constructed in accordance with the in vention;

Fig. 2 is a similar section through a modified embodiment of the invention; while gas discharges. Fig. 1 shows a closing wall of a glow discharge chamber (shown more'fully in Fig. 3).into which the current lead-in is to be introduced. A double walled bottom 1, 2 provides a cooling space 3 'th'roughwhich passes a cooling medium. Through the vessel wall 1, 2

acting as one electrode there passes a'secondelectrpde 4 provided with a screw-threaded attachment 5 for securing the work-pieces to be treated, the electrode pass; ing through an insulator 6 provided onthe outside 0;

the vessel. The electrode 4 is cooled by a cooling means entering at 7 and leaving at 8 so that the electrode 4 is cooled over the whole of its length. A screw-cap 9.

presses the insulator 6 against a packing 10 which is provided in the screw-threaded connector 11 of the bottom of the vessel. The packing 10 may consist of rubber, artificial resins, and the like. The packing 10 is supported partly against a flange'25 of the electrode 4, partly against a solid insulator 20 which, in its turn, abuts with one shoulder against the vessel wall. The

insulator 20 does not project into the interior of the ves-.

sel and is covered at its inner end by a metalring 13, which tightly surrounds the electrode 4. A gap isprovided between the metal ring 13 and the inner part 1 of the vessel wall, which is strengthened by a ring 14. The width of this gap is so narrow at its lower end, viz. where the ring 13 abuts against the insulator 20, that a glow discharge cannot occur in it at a gas pressure of 1 mm. Hg and less, or is so weakened that it does not cause any disturbance. In practice gap widths of the order of 1 mm. or of a few tenths of a mm. are used. This gap, which thus reaches from approximately the up per edge of the insulator 20 to the interior of the vessel, widens towards the interior of the vessel gradually in such a way that at its inner end, i.e., at the point at which it opens into the interior of the chamber, its width is a multiple of the width in the proximity of the insulator 20. The widening of the gap 15 takes place along a portion that is approximately half the total length of the gap extending between the metal wall parts. The

gap 15 is followed immediately by a gap 23, which lies between the vessel wall 1, 2 and the insulator 20. The gap 23 has the same width as the lower part of the gap, 15 so that these gapspass'smoothly into one another. An annular enlargement 24 of the gap is provided at the boundary between the two gaps 15 and 23 for the protection of the insulator 29.

Figure 2 shows, by way of example a second embodiment of the invention which differs from the arrangement shown in Figure l in that a narrow gap 18a is provided between the insulator 20 and the wall of the vessel. This gap is continued by the gap 19, which is of gradually increasing width and opens into the widened space of the annular slits 22a and 22b by gradual enlargement. A narrow gap 18b is provided in front of the enlarged space 22a and 22b and communicates therewith, which gap 18b is bounded by the metal ring 13 of the one elec trode 4 and the metal ring 14 of the vessel wall 1, and opens into the vessel space 12.

Fig. 3 illustrates diagrammatically a glow discharge chamber equipped with the lead-in device of the present invention. The cooling space 3 of the jacketed wall of the chamber, indicated at 1, 2, receives the cooling agent through the connection 33, the cooling agent being discharged at 34. The workpiece is shown at 30 (for example, in the form of an automobile piston) and is mounted by way ofthe rod 31 and threaded stud 32 in the threaded"support 5, which is secured to the inner conductor 4 of the lead-in. The interior space 12 of the chamber 1, after the chamber, has been evacuated, is supplied with a suitable. gaseous atmosphere at the requiredsub-pressure by way of the supply conduit 35 and discharge conduit 36. At, the terminal 37, the inner conductor 4' is conniected, withthe source of direct or alternating current, while the metal wall 1, 2 is similarly connected. to the source of current by way of the terminal 38.

What we claim isi 1. In a metallic gas discharge vessel, a current leadin for conducting an operating potential to a workpiece supported .within the vessel, said lead-in including a metallic inner electrode adapted to be connected to the workpiece, the, wall of said vessel and-said inner elecreddening; subjected in operation to different electric pdten'tialssaid inner, electrode being surrounded along amnion there'ofjby a metallic part connectedto the ves'f. sci with. a narrow annular gapbetween the electrode and said pjan. said gap constituting a protecting gap between the inner. electrode and the metal part of the vessel and being defined by parallel walls at the rear portion thereof, said gap opening at its front end into the interior of the vessel and at its rearward end being closed by an insulating sleeve engaging the inner electrode, at least one of the metal walls bounding the gap, along a portion or its axial length, being increasingly curved away with increasing approach to the mouth of the gap in the interior of the chamber from the other metal wall opposite the same, whereby a gap portion widening continuously toward the mouth of the gap is formed, the widest part of the gap defined by the non-parallel metallic walls having a radial width which is at least equal to twice the radial width of that part of the gap in which the metal walls run parallel to each other. i

2. An arrangement as claimed in claim 1, wherein the radial dimension of the gap in that portion of the gap in which the bounding walls are parallel to each other is from several tenths of a millimeter to l millimeter.

3. An arrangement as claimed in claim 1, wherein the width of the gap at its widest part is a multiple of its width at the narrowest part.

4. An arrangement as claimed in claim 1, wherein the gap opens at its part having substantially constant width into an adjacent transverse gap.

,5. An arrangement as claimed in claim 1, wherein the said wider space opens into an additional gap which has silbstantially the same axial width as the radial width of,the part of the gap which is of substantially constant width.

6. An arrangement as claimed in claim 1, wherein the inner portion of the insulator is spaced from the adjoin- 4 ing anode by a gap which connects with the first-mentioned gap;

7. An arrangement as claiined in claim 1, wherein the first-mentioned gap widens toward the interior of the vessel, and wherein a transverse gap leads from the first gap and extends into at least one of the electrodes.

8. In a glow discharge vessel having metallic walls serving as an electrode in a gas discharge within the vessel, a second electrode passing through the wall of the vessel and spaced therefrom and extending' into the interior of the vessel, an insulating member surrounding the second electrode and in contact with the wall of the vessel and acting to space and insulate the second elec trode from the wall of the vessel, the outer surface of that end portion of the insulating member which faces in the direction of the interior of; the vessel being spaced from the adjacent vessel wall to provide a gap, and concentric metallic ringsspaced from each other and conductingly secured, respectively, to the. wall or the vessel and to, the inner portion of; the second electrode, such spacing, providing a gap which communicates with the first mentioned gap, the combined gap including along its length a gap portion of gradually increasing width in the directionof the interior of the vessel, the maximum 1 width of such gap portion being at least equal to twice the width of the narrowest portion of the gap.

9. An arrangement according to claim 8, wherein the gap portion of gradually increasing width is at the inner end of the combined gap and opens into the interior of the discharge vessel.

10. An arrangement according to claim 8,, wherein the gap portion of gradually increasing width is disposed intermediate the ends of the combined gap, and within the region bounded by metallic partsof the wall of the chamber and of the second electrode, said metallic parts being shaped to provide a further gap extendingtransversely to the combined gap, the forward end of the gap portion of increasing width debouching into said further gap. I

References Cited in the file of this patent UNITED STATES PATENTS 

